Fabric and yarn structures for improving signal integrity in fabric-based electrical circuits

ABSTRACT

Coaxial and twisted pair conductive yarn structures reduce signal crosstalk between adjacent lines in woven electrical networks. A coaxial conductive yarn structure includes an inner conductive yarn having a plurality of conductive strands twisted together. An outer conductive yarn is wrapped around the inner conductive yarn. An insulating layer separates the inner and outer yarns. A twisted pair conductive yarn structure includes first and second conductive yarns, each including a plurality of conductive strands being twisted together. The first and second conductive yarns are twisted together to form a helical structure. In a woven electrical network, at least one conductor of adjacent conductive yarn structures is connected to ground to reduce signal crosstalk. Coaxial and twisted pair yarn structures may also be formed simultaneously with weaving or knitting the threads that make up the structures into a fabric.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/609,074, filed Jun. 27, 2003, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/392,591, filed Jun. 28, 2002and U.S. Provisional Patent Application Ser. No. 60/447,438, filed Feb.14, 2003, the disclosures of each of which are incorporated herein byreference in their entireties.

GOVERNMENT INTEREST

This invention was made with U.S. Government support under Grant No.N39998-98-C3566 awarded by the Department of Defense-Defense AdvancedResearch Projects Agency. The U.S. Government has certain rights in theinvention.

TECHNICAL FIELD

The present invention relates to methods and systems for improvingsignal integrity in fabric-based electrical circuits. More particularly,the present invention relates to new fabric and yarn structures andmethods for making the same for solving signal integrity relatedproblems, such as crosstalk, in woven or knitted electrical networks.

BACKGROUND ART

The demand for flexible electrical circuits and circuit boards isincreasing in the fields of electronics and computer engineering.Circuit boards have traditionally been rigid structures that usepolymeric or epoxy-based material as the dielectric. Copper wiring orinterconnect patterns are inscribed on the circuit boards usingphotolithography or electron beam lithography to obtain a desired wiringpattern. Using rigid circuit boards may not be desirable in allapplications as they are inflexible and non-conformable and also due tothe fixed volume occupied by such circuit boards.

In response to the problems associated with conventional rigid circuitboards, flexible circuit boards have been developed. One type offlexible circuit board that has been developed includes textiles-basedcircuit boards. Textiles-based circuit boards and the correspondingelectrical circuits include both conductive fibers and nonconductivefibers. The conductive fibers can be used to interconnect electricalcomponents to form an electrical circuit. A fabric-based electricalnetwork can be incorporated into a garment and worn by the user. Suchnetworks have applications in the fields of medicine, communications,electronics, automobiles, and space exploration. One recent applicationof fabric-based electrical networks is uniforms for military personnel.

One problem with fabric-based electrical networks is AC signal crosstalkbetween adjacent conductors. When conductors in fabric-based electricalnetworks are placed parallel and close to each other (though not indirect contact with each other), capacitive and inductive signalcrosstalk between neighboring lines can occur. Such crosstalk leads todistortion of signals in neighboring lines that carry electricalsignals. In addition, on quiet lines adjacent to a signal-carrying line,crosstalk can cause peaks or troughs due to the rise and fall andelectrical signals on the signal-carrying line.

In light of these problems associated with conventional fabric-basedelectrical networks, there exists a need for improved methods andsystems for improving signal integrity in fabric-based electricalcircuits.

DISCLOSURE OF THE INVENTION

The present invention includes conductive yarn structures and fabricscontaining conductive yarn structures for improving signal integrity infabric-based electrical circuits. As used herein, the term “conductiveyarn” is intended to refer to a group of conductive strands that aretwisted together to form a single conductor and exhibiting sufficientflexibility, conformability, resiliency, bending characteristics, andrecovery required for fabric-based circuits to be incorporated inwearable garments. Examples of conductive strand material suitable forforming conductive yarns includes copper, steel, gold, aluminum, silver,iron, any of the alloys from the above mentioned materials, andconductive polymers (inherently conductive polymeric materials, such aspolypyrrole, polyacetylene, polythiophene and polyaniline, dopedconductive polymeric materials, carbon black-doped/impregnated polymericyarns, metal coated polymeric yarns or fibers and conductive yarns ofsuitable types). The term “yarn” is intended to refer to a group ofstrands (like filaments, fibers, or fine wires) being twisted togetherto form a single structure. These strands may be continuous ornon-continuous along the length of the twisted yarn. A yarn may consistof only one continuous strand (monofilament yarn). In the case ofmonofilament yarns, the term “yarn” includes filaments and fibers. Inthe case of monofilament yarns, the term “yarn” includes only very finewires i.e. with a wire diameter (i.e. monofilament yarn diameter) lessthan 20 microns. The term “yarn” is not intended to include conventionalwires. As indicated above, the term “yarn,” as used herein, refers to astructure that exhibits sufficient flexibility, conformability,resiliency, bending characteristics, and recovery required forfabric-based circuits to be incorporated in wearable garments.Conventional wires lack one or more of these characteristics, makingthem unsuitable for incorporation in a fabric. The individual strandsforming the yarn may be very fine wires (twisted to form the yarn) butthe diameter of these fine wires should ideally be less than 20 micronsto provide sufficient flexibility and conformability of the yarn(twisted strand structure).

One conductive yarn structure of the present invention is a coaxialconductive yarn structure. In a coaxial conductive yarn structure, afirst conductive yarn extends in a first direction and has a pluralityof conductive strands that are twisted together. An insulating layersurrounds the conductive strands. A second conductive yarn, which alsohas a plurality of conductive strands being twisted to each other, iswrapped around the insulating layer in a second direction transverse tothe first direction. An insulating layer may surround the secondconductive strand.

Another conductive yarn structure suitable for reducing crosstalk in afabric-based electrical network is a twisted pair conductive yarnstructure. A twisted pair conductive yarn structure includes a firstconductive yarn having a plurality of conductive strands being twistedtogether (and also having an insulating layer surrounding the twistedstrands). An insulating layer surrounds the conductive strands. A secondconductive yarn, also having a plurality of strands being twistedtogether, is twisted together with the first conductive yarn to form ahelical structure.

In a woven electrical network including coaxial conductive yarnstructures, first and second coaxial conductive yarns are woven(parallel to each other but separated from each other by non-conductingyarns) into a fabric in one direction. The inner conductive yarn of oneof the conductive yarn structures may be connected to a signal source.The outer conductive yarn of one or both of these coaxial conductiveyarn structures may be connected to ground. When an AC signal is appliedto the inner conductor of the first coaxial conductive yarn structure(and/or the inner conductor of the second coaxial conductive yarnstructure), the outer conductive yarns of the first and second coaxialconductive yarn structures are grounded and block electromagnetic fieldsemanating from the inner conductive yarn of the first coaxial conductiveyarn structure and thereby reduce crosstalk between the first and secondcoaxial conductive yarn structures. In a woven electrical network onemay also have multiple (more than two) strands of coaxial conductiveyarn structures woven into the fabric in one or two of the orthogonaldirections (warp and weft directions) of the woven fabric.

As used herein, the term “electrical network” may be usedinterchangeably with the term “electrical circuit”.

Another woven electrical network of the present invention includes firstand second twisted pair conductive yarn structures. Each of the firstand second twisted pair conductive yarn structures is woven to a fabricin a first direction. One conductor in each of the twisted pairconductive yarn structures is connected to ground. The other conductorin at least one of the twisted pair conductive yarn structures isconnected to an AC signal source. When the AC signal is applied to theconductor, the grounded second conductors of the twisted pair conductiveyarn structures block electromagnetic fields emanating from the firstconductive yarn of the first twisted pair conductor and thereby reducecrosstalk between the first and second twisted pair conductive yarnstructures.

According to another aspect, the present invention includes methods andsystems for creating conductive thread structures with improvedcrosstalk resistance while the thread structures are being woven orknitted into a fabric. For example, a coaxial structure may be createdby leno weaving conductive threads into a fabric. A similar process maybe used to create a twisted pair structure while leno weaving the yarnsthat make up the twisted pair structure into a fabric. One advantage ofcreating the structures while the structures are being woven or knittedinto a fabric is that the time required to produce such structures isreduced over methods where coaxial or twisted pair structures are formedin advance of making the fabric. Another advantage of forming thestructures during the knitting or weaving process is that the weavingcan be altered during the formation of the structures to create floatsfor selective electrical connection and disconnection.

As used herein, the term “thread” may be used interchangeably with theterm “yarn”.

Accordingly, it is an object of the invention to provide improvedmethods and systems for reducing crosstalk in fabric-based circuits.

It is another object of the invention to provide improved conductiveyarn structures for improving signal integrity in fabric-basedelectrical circuits.

It is another object of the invention to provide methods for makingcoaxial and twisted pair structures while the structures are beingknitted or woven into a fabric.

Some of the objects of the invention having been stated hereinabove,other objects will become evident as the description proceeds when takenin connection with the accompanying drawings as best describedhereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be explained withreference to the accompanying drawings of which:

FIG. 1 is a perspective view of a coaxial conductive yarn structure forimproving signal integrity in fabric-based electrical networks accordingto an embodiment of the present invention;

FIG. 2 is a perspective view of a twisted pair conductive yarn structurefor improving signal integrity in a fabric-based electrical networkaccording to an embodiment of the present invention;

FIG. 3 is a top view of a fabric-based electrical network includingfirst and second coaxial conductive yarn structures according to anembodiment of the present invention;

FIG. 4 is a top view of a fabric-based electrical network includingfirst and second twisted pair conductive yarn structures according to anembodiment of the present invention;

FIG. 5 is a top view of a fabric-based signal transmission system inwhich conductive yarn structures are woven as warp threads into a fabricand twisted around consecutive weft threads to form a spiral pairaccording to an embodiment of the present invention;

FIG. 6 is a top view of a fabric-based signal transmission system inwhich a bottom doup warp thread goes over consecutive weft threads andcrosses adjacent warp threads between two weft threads according toembodiment of the present invention;

FIG. 7 is a top view of a fabric-based signal transmission system inwhich insulated conductive yarns are woven in a leno weave to form atwisted pair configuration according to an embodiment of the presentinvention;

FIG. 8 is a top view of a fabric-based signal transmission system inwhich conductive threads are woven in a leno weave to form twisted pairconfigurations separated by nonconductive fibers being plain woven intoa fabric according to an embodiment of the present invention;

FIG. 9 is a top view of a fabric-based signal transmission system inwhich one thread of a conductive warp thread twisted pair is connectedto an AC signal source and the other thread is connected to groundaccording to an embodiment of the present invention;

FIG. 10 is a top view of a fabric-based signal transmission system inwhich insulated conductive threads are woven in a leno weave to formtwisted pair like structures and wherein the threads include floatsand/or woven portions to facilitate electrical connection anddisconnection or electrical device attachment;

FIG. 11 is a top view of a fabric-based signal transmission systemillustrating a crossover point between a leno woven twisted pairstructure in the warp direction and a woven or floating twisted pairstructure in the weft direction according to an embodiment of thepresent invention;

FIG. 12 is a top view of a fabric-based signal transmission system inwhich conductive threads are leno woven into a fabric to form a coaxialstructure according to an embodiment of the present invention;

FIG. 13 is a top view of a fabric-based signal transmission system inwhich conductive threads are leno woven into a fabric to form a coaxialstructure and in which the threads include floating portions or wovenportions to facilitate electrical device attachment or to facilitateelectrical connection and disconnection according to an embodiment ofthe present invention;

FIG. 14 is a top view of a warp knitted fabric structure;

FIG. 15 is a top view of fabric-based signal transmission system inwhich conductive threads are warp knitted into a fabric to form atwisted pair structure according to an embodiment of the presentinvention;

FIG. 16 is a top view of a fabric-based signal transmission system inwhich conductive threads are warp knitted into a fabric to form acoaxial structure according to an embodiment of the present invention;

FIG. 17 is a top view of a fabric-based signal transmission system inwhich conductive threads are weft knitted into a fabric to form atwisted pair structure according to an embodiment of the presentinvention;

FIG. 18 is a top view of a fabric-based signal transmission system inwhich conductive threads are weft knitted into a fabric to form acoaxial structure according to an embodiment of the present invention;

FIG. 19 is a top view of a fabric-based signal transmission system inwhich a coaxial conductive yarn structure is warp knitted into a fabricaccording to an embodiment of the present invention;

FIG. 20 is a top view of a fabric-based signal transmission system inwhich a coaxial conductive yarn structure is weft knitted into a fabricaccording to an embodiment of the present invention;

FIG. 21 is a top view of a fabric-based signal transmission system inwhich a twisted pair conductive yarn structure is warp knitted into afabric according to an embodiment of the present invention;

FIG. 22 is a top view of a fabric-based signal transmission system inwhich a twisted pair conductive yarn structure is weft knitted into afabric to form a coaxial structure according to an embodiment of thepresent invention;

FIG. 23 is a top view of a fabric-based signal transmission system inwhich signal carrying conductive threads are separated by groundedconductors;

FIGS. 24A and 24B illustrate multi-layered fabric-based signaltransmission systems according to embodiments of the present invention;

FIG. 25 is a perspective view of an insulated conductive yarn structuresurrounded by a braided outer conductor according to an embodiment ofthe present invention;

FIG. 26 is a top view of a fabric-based signal transmission system inwhich braided coaxial yarn structures are woven parallel to each otherin a fabric according to an embodiment of the present invention;

FIG. 27 is a top view of a fabric-based signal transmission system inwhich a braided coaxial yarn is warp knitted into a fabric according toan embodiment of the present invention;

FIG. 28 is a top view of a fabric-based signal transmission system inwhich a braided coaxial yarn is weft knitted into a fabric according toan embodiment of the present invention;

FIG. 29 is a top view of a fabric-based signal transmission systemincluding a plurality of coaxial conductive yarn structures beingbraided into a fabric according to an embodiment of the presentinvention;

FIG. 30 is a top view of a fabric-based signal transmission systemincluding a plurality of twisted pair conductive yarns being braidedinto a fabric according to an embodiment of the present invention;

FIG. 31 is a top view of a fabric-based signal transmission systemincluding a plurality of braided coaxial conductive yarn structuresbeing braided into a fabric according to an embodiment of the presentinvention;

FIG. 32 is a top view of a fabric-based signal transmission systemincluding a woven fabric having a plurality of braided conductive yarnstructures according to an embodiment of the present invention;

FIG. 33 is a top view of a fabric-based signal transmission systemincluding a warp-knitted fabric having a plurality of braided conductiveyarn structures according to an embodiment of the present invention; and

FIG. 34 is a top view of a fabric-based signal transmission systemincluding a weft-knitted fabric having a plurality of braided conductiveyarn structures according to an embodiment of the present invention

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes conductive yarn structures for improvingsignal integrity in fabric-based electrical networks. FIG. 1 illustratesan example of one conductive yarn structure suitable for improvingsignal integrity in fabric-based electrical networks according to anembodiment of the present invention. Referring to FIG. 1, a conductiveyarn structure 100 comprises a coaxial conductive yarn structure.Coaxial conductive yarn structure 100 includes an inner conductive yarn102 surrounded by an insulating layer 104 and an outer conductive yarn106, which is preferably also surrounded by an insulating layer 108.Inner conductive yarn 102 includes a plurality of conductive strandsbeing twisted together. The conductive strands may be made of anysuitable conductive material, such as such as copper, gold, steel,aluminum, silver, or iron or conductive polymers (inherently conductivepolymeric materials, such as polypyrrole, polyacetylene, polythiopheneand polyaniline, doped conductive polymeric materials, carbonblack-doped/impregnated polymeric yarns, metal coated polymeric yarns orfibers and conductive yarns of all different kinds). Outer conductiveyarn 106 also includes a plurality of strands being twisted together. Inone example, outer conductive yarn 106 may be made of silver-coatednylon or any of the above-mentioned conducting materials. Insulatinglayers 104 and 108 may be made of any suitable insulating material, suchas polyvinylchloride; rubber; rubber forming polymers, includingpolyisoprene, polybutadiene, polychloroprene, and polyisobutylene;polyesters; polyolefins; and polyamides. In one example, insulatinglayers 104 and 108 may be made of polyvinylchloride.

It is important to note that structures 102 and 106 are yarns, ratherthan wires. The term “yarn” is defined above and is not intended toinclude conventional wires. As indicated above, the term “yarn,” as usedherein, refers to a structure that exhibits sufficient flexibility,conformability, resiliency, bending characteristics, and recoveryrequired for fabric-based circuits to be incorporated in wearablegarments. Conventional wires lack one or more of these characteristics,making them unsuitable for incorporation in a fabric. The individualstrands forming the yarn may be very fine wires twisted to form theyarn, but the diameter of these fine wires should ideally be less than20 microns to provide sufficient flexibility and conformability of theyarn or twisted strand structure.

Coaxial conductive yarn structure 100 may be constructed by firstforming inner and outer conductive yarns 102 and 106. These yarns may beformed using conventional yarn twisting techniques. Once the inner andouter conductive yarns are formed, insulating layers 104 and 108 may beapplied to either or both yarns. Inner conductive yarn 102 and outerconductive yarn 106 may then be fed into a yarn covering machine or ayarn wrapping machine. The yarn covering or wrapping machine may wind orwrap outer conductive yarn 106 around inner conductive yarn 102. A yarncovering machine used for wrapping a yarn around an elastomeric coreyarn could be used to develop the coaxial yarn structure. In that case,in order to reduce the likelihood of breakage, the wrapping speed of theyarn covering machine is preferably reduced over that used for wrappingelastomeric yarns. The wrapping of conductive yarns 106 around theconductive yarn 102 can also be carried out using a yarn twistingmachine (for example, a ring twister) to wrap yarn 106 with insulation108 around yarn 102 with insulation 104.

FIG. 2 illustrates another example of a conductive yarn structuresuitable for improving signal integrity in a fabric-based signaltransmission system according to an embodiment of the present invention.Referring to FIG. 2, conductive yarn structure 200 comprises a twistedpair conductive yarn structure. Twisted pair conductive yarn structure200 includes first and second conductive yarns 202 surrounded byinsulating layers 204 and being twisted together to form a helicalstructure. Conductive yarns 202 are preferably made of multiple strandsof a conductive material, such as such as copper, gold, steel, aluminum,silver, iron, any of the alloys from the above mentioned materials, andconductive polymers (inherently conductive polymeric materials, suchpolypyrrole, polyacetylene, polythiophene and polyaniline, dopedconductive polymeric materials, carbon black-doped/impregnated polymericyarns, metal coated polymeric yarns, or fibers and conductive yarns ofall different kinds). As with the coaxial structure described above, themultiple strands are preferably twisted together to form a yarn.Insulating layer 204 may be made of any suitable insulating material,such as polyvinylchloride; rubber; rubber forming polymers, includingpolyisoprene, polybutadiene, polychloroprene, and polyisobutylene;polyesters; polyolefins; and polyamides. The strands that formconductive yarns 202 may be twisted together using a conventional yarntwisting machine, as described above. Once conductive yarns 202 havebeen formed, insulating layers 204 are preferably added to conductiveyarns 202. Conductive yarns 202 are preferably then twisted into ahelical structure using a yarn twisting machine.

FIG. 3 illustrates an example of a woven electrical network includingcoaxial conductive yarn structures according to an embodiment of thepresent invention. In the illustrated example, woven electrical network300 includes coaxial conductive yarn structures 100. Coaxial conductiveyarn structures 100 are incorporated in woven electrical network 300 andextend in a direction parallel to each other. For example, coaxialconductive yarn structures 100 may be weft or warp yarns or both woveninto a fabric.

According to an important aspect of the invention, outer conductors 106of coaxial conductive yarn structures 100 are preferably connected toground 302. In a preferred embodiment of the invention, outer conductors106 may be welded to a signal ground at a fabric crossover point, forexample, as described in commonly-assigned, co-pending U.S. patentapplication Ser. No. 10/041,248 filed Jan. 8, 2002, the disclosure ofwhich is incorporated herein by reference in its entirety. Connectingouter conductors 106 to ground blocks electromagnetic fields emanatingfrom inner conductors 102. This blocking reduces crosstalk betweenadjacent conductive yarn structures and improves signal integrity. An ACsignal source 304 may be connected to one or both of inner conductiveyarns 102 of the coaxial conductive yarns structures. The AC signalsource may be any suitable signal source, depending on the particularapplication. A plurality of nonconductive fibers 306 may be included inthe fabric along with coaxial conductive yarn structures 100. In oneexample, nonconductive fibers 306 comprise nylon yarns.

In operation, AC signal source 304 applies a signal to inner conductiveyarn 102. Electromagnetic fields emanate from inner conductive yarns102. However, grounded outer conductive yarns 106 block these fields andthereby prevent crosstalk on adjacent lines.

In order to make a woven electrical network, such as that illustrated inFIG. 3, coaxial conductive yarn structures 100 and nonconductive fibers306 may be fed into a loom as warp yarns, weft yarns, or both. In theillustrated example, coaxial conductive yarn structures 100 extend in adirection parallel to each other in woven electrical network 300. Anexample of a loom suitable for weaving coaxial conductive yarnstructures 100 into a loom is an Eltex loom with Staubli Jacquard heads.

FIG. 4 illustrates yet another example of a woven electrical networkincluding conductive yarn structures designed to reduce crosstalkbetween adjacent lines and to improve signal integrity. In FIG. 4,twisted pair conductive yarn structures 200 are woven into a fabric toform a woven electrical network 400. For example, twisted pairconductive yarn structures 200 may be woven into the fabric as warpyarns, weft yarns, or both. In the illustrated example, twisted pairconductive yarn structures 200 extend in a direction parallel to eachother in woven electrical network 400. Woven electrical network 400 maybe made by feeding twisted pair conductive yarn structures andnonconductive fibers 306 into any suitable loom such as a Jacquard loom,as described above.

In one mode of operation of the twisted pair conductive yarn structures200 in woven electrical network 400, one conductor 202 of each twistedpair conductive yarn structure is connected to ground 302. The otherconductor 202 of at least one of the twisted pair conductive yarnstructures is connected to an AC signal source 304. Connections betweenconductors 202 and ground and signal source 304 may be made usingwelding, as described in the above-referenced commonly-assignedco-pending U.S. patent application. In operation, when AC signal source304 applies an AC signal to conductor 202, the grounded conductors blockelectromagnetic fields emanating from signal-carrying conductor 202. Asa result, crosstalk between twisted pair conductive yarn structures 200is reduced. In another mode of operation of the twisted pair threads,the two conductive threads 202 are oppositely driven by an AC signalsource. Driving conductive threads of a twisted pair structure withequal but opposite AC signals results in common mode noise rejection.Either mode of operation is intended to be within the scope of theinvention.

Although the examples in FIGS. 3 and 4 illustrate coaxial and twistedpair conductive yarn structures in separate fabrics, it is understoodthat these structures can be incorporated into the same fabric. Anysuitable combination of coaxial and twisted pair conductive yarnstructures is intended to be within the scope of the invention.

Fabric Structures to Improve Signal Integrity Leno Weave Structures

In addition to the coaxial and twisted pair conductive yarn structuresdescribed above, the present invention may also include fabricstructures in which both coaxial and twisted pair structures can beformed while a fabric is being knitted or woven. Forming coaxial andtwisted pair structures as a fabric is being knitted or woven improvesmanufacturing efficiency in making fabric-based signal transmissionsystems and facilitates creation of floats for electrical deviceconnection and disconnection and for electrical device attachment.

FIG. 5 illustrates an example of a fabric-based signal transmissionsystem 500 in which twisted pair structures can be formed while thefabric is being woven according to an embodiment of the presentinvention. Referring to FIG. 5, a plurality of warp threads 502 and 504are twisted around consecutive weft threads 506. This type ofconfiguration is referred to in the textiles industry as a leno weave. Aleno weave involves pair-wise crossing of adjacent warp threads in awoven fabric. A leno weave is a form of plain weave in which adjacentwarp threads are twisted around consecutive weft threads to form aspiral pair, effectively locking each weft in place. According to thepresent invention, warp threads 502 and 504 are preferably insulatedconductive threads or yarns. Leno weaving conductive warp threads in themanner shown in FIG. 5 produces twisted pair conductive yarn structures,which exhibit common mode noise rejection when threads 502 and 504 areoppositely driven by an AC signal source. In another mode of operationof the fabric-based signal transmission system 500 containing leno-woventwisted pair conductive yarn structures, one conductor 502 of eachleno-woven twisted pair conductive yarn structure is connected toground. The other conductor 504 of at least one of the leno-woventwisted pair conductive yarn structures is connected to an AC signalsource.

According to an important aspect of the invention, the twisted pair yarnstructures formed by threads 502 and 504 can be accomplished during theweaving process by the use of leno headles, which allows control ofindividual warp yarns. In FIG. 5, warp threads 502 and 504 crossnonconductive threads 506 on alternating sides. However, the presentinvention is not limited to forming twisted pair conductive yarnstructures using only this type of leno weave. Any suitable leno weavein which twisted pair or coaxial structures can be formed while a fabricis being woven is intended to be within the scope of the invention.

FIG. 6 illustrates a fabric-based signal transmission system 600 inwhich twisted pair structures are formed using a bottom doup leno weave.In a bottom doup leno weave, the doup warp thread goes over consecutiveweft threads and crosses below the adjacent warp thread between two weftthreads. In FIG. 6, threads 602 and 604 are preferably insulatedconductors. Threads 606 may be conductive or nonconductive. If threads606 are conductive, they are preferably insulated. In the configurationillustrated in FIG. 6, thread 604 is the doup warp thread that passesover consecutive weft threads 606 and below warp thread 602 betweenadjacent weft threads 606. By using a bottom doup leno weave, thetwisted pair structures can be formed by conductors 602 and 604 at thesame time conductors 602 and 604 are being woven into a fabric. Asstated above, this increases the efficiency with which fabric-basedsignal transmission systems with improved signal integritycharacteristics can be manufactured.

The present invention is not limited to forming twisted pair and coaxialstructures using a bottom doup leno weave. In an alternate embodiment ofthe invention, the twisted pair structures can be formed using a topdoup leno weave. In case of top doups, the doup warp thread goes belowconsecutive weft threads and crosses above the adjacent warp thread (theground threads) in between two weft threads. Twisted pair and coaxialstructures of the present invention can also be formed with the doupthread going above and below the consecutive weft threads but alwaysbeing above the adjacent warp threads in order to form a spiral pair, asillustrated in FIG. 5. In addition, the fabric-based signal transmissionsystems of the present invention that are made using a leno weave can becombined with other weaving techniques to from a wearable garment withone or more electrical circuits.

It should be noted that in the twisted pair structures described herein,one conductor may be connected to an AC or DC signal source and theother conductor may be grounded, similar to a coaxial signaltransmission system in which the inner conductor carries a signal andthe outer conductor is grounded. In an alternate mode of operation, theconductors in a twisted pair structure may be oppositely driven by an ACsignal source. Either mode of operation is intended to be within thescope of the invention.

In the leno-woven twisted pair structures described herein, either orboth of the conductive threads that form the twisted pair structure maybe insulated conductive yarns, as illustrated in FIG. 2. FIG. 7illustrates this concept. In FIG. 7, a fabric-based signal transmissionsystem 700 includes insulated conductive threads 702 and 704 being lenowoven into a fabric with weft threads 706, which may be conductive(preferably insulated conductive threads especially if either one ofthreads 702 or 704 is not insulated) or nonconductive. Each thread 702and 704 may include a plurality of inner conductive strands beingtwisted together to form a conductive yarn 202 and may be coated with anouter insulating layer 204.

As stated above, the leno weaving may be combined with other types ofweaving techniques to form a garment incorporating one or moreelectrical circuits. FIG. 8 illustrates a fabric-based signaltransmission system 800 where twisted pair structures are leno woven ina fabric, and the fabric includes a plain woven portion. In FIG. 8,threads 802 and 804 are preferably insulated conductive threads, asdescribed above. Threads 810 and 812 may be conductive or nonconductive.In the illustrated example, threads 802 and 804 are leno-woven into thefabric and form a twisted pair structure. Similarly, threads 806 and 808are leno-woven into the fabric to form an additional twisted pairstructure. However, threads 810 are plain woven into the fabric. Such acombination weave may be formed on a Jacquard loom where threads areindividually addressable.

As stated above, in one mode of operation, one insulated conductivethread forming the spiral pair of a leno weave may be connected toground and the other conductive thread may be connected to a signalsource, such as an AC signal source. FIG. 9 illustrates this mode ofoperation. In FIG. 9, conductive threads 804 and 808 are connected to ACsignal supplies 900 and conductive threads 802 and 806 are connected toground 902. In this arrangement, AC signal crosstalk between conductivethreads 804 and 808 is significantly reduced. As a result, using thisconfiguration, the density of fabric-based signal transmission systemscan be increased, which increases the functionality that can be providedby fabric-based electrical circuits. In addition, because the twistedpair structure is formed using a leno weave, rather than separatelyweaving the twisted pair structure and then weaving the twisted pairstructure into the fabric, manufacturing time is reduced.

Another advantage of forming twisted pair structures while weaving afabric is that the twisting of the conductive threads can be controlledto form floats in regions of the fabric to facilitate electricalconnection and disconnection and also electrical device attachment. FIG.10 illustrates an example of a fabric-based signal transmission system1000 including floats according to an embodiment of the presentinvention. In FIG. 10, threads 1002-1008 are preferably insulatedconductive threads, as described above. Threads 1010 and 1012 may beconductive or nonconductive. Threads 1006 and 1008 are leno-woven intothe fabric to form a twisted pair structure. Similarly, threads 1002 and1004 are leno-woven into the fabric to form an additional twisted pairstructure. Threads 1002 and 1006 each include a floating region 1014 tofacilitate electrical connection and disconnection and also tofacilitate electrical device attachment. Threads 1004 and 1008 eachinclude a plain-woven region 1016, rather than a floating region, sothat the threads can be separately identified when making electricalconnections and disconnections. Threads 1004 and 1008 may also eachinclude a floating region 1014 to facilitate electrical connection anddisconnection and also to facilitate electrical device attachment.

As mentioned above, electrical connection in a fabric-based signaltransmission system may be performed by welding conductive threads atcrossover points, which may correspond to floats. Electricaldisconnection may be effected by cutting conductive threads at thefloats. FIG. 11 illustrates a signal transmission system 1100 includinga crossover point at which electrical connection or disconnection can bemade. In FIG. 11, threads 1102-1108 are assumed to be insulatedconductors. Threads 1110 may be conductive or nonconductive. Conductivethreads 1102 and 1104 may be a pre-formed twisted pair structure. Incontrast, conductive threads 1106 and 1108 are a twisted pair structurethat was created while conductive threads 1110 were being leno woveninto the fabric. It can be seen that conductive threads 1102 and 1104intersect conductive threads 1106 and 1108 at a crossover point 1112. Byselectively dissolving the insulating layers on the conductive threadsand welding conductors together, electrical connection betweenorthogonal conductive threads can be achieved. In addition, it may bedesirable to weld all of the crossover points in a fabric. In such anexample, electrical circuits can be created by selectively disconnectingby cutting floats on appropriate sides of the crossover points.

In addition to producing signal transmission systems with twisted pairstructures simultaneously with weaving conductive threads into a fabric,coaxial structures can also be produced while weaving conductive threadsinto a fabric. FIG. 12 illustrates an example of a coaxial structurethat can be produced while weaving conductive threads into a fabricaccording to an embodiment of the present invention. In FIG. 12, afabric-based signal transmission system 1200 includes insulatedconductive threads 1202, 1204, and 1206 and threads 1208, which may beconductive or nonconductive. Conductive threads 1202, 1204, and 1206 areleno-woven into the fabric to form a coaxial structure. This structurecan be formed at the time threads 1202, 1204, and 1206 are being woveninto the fabric by using a Jacquard loom equipped with leno headles.Because the coaxial structure can be formed at the time the fabric iscreated, the time and cost required to manufacture garments includingcoaxial structures is reduced. In addition, as described above, formingthe coaxial structures at weaving time facilitates production offloating regions for electrical connection and disconnection and alsoelectrical device attachment.

In operation, conductor 1206 may be connected to an AC signal source andconductors 1202 and 1204 may be connected to ground. Connectingconductors 1202 and 1204 to ground reduces the likelihood that externalelectromagnetic interference will affect the signal on conductor 1206.Connecting conductors 1202 and 1204 to ground also reduces thelikelihood that the signal on conductor 1206 will adversely affectsignals on other conductors. As a result, signal conductors can beplaced close to each other in a fabric and component density can beincreased.

As with the twisted pair structures described above, floats can beformed in coaxial structures to facilitate electrical connection anddisconnection. FIG. 13 illustrates and example of a coaxial structurewith floats according to an embodiment of the present invention. In FIG.13, a fabric-based signal transmission system 1300 includes insulatedconductive threads 1302, 1304, and 1306, which are leno woven in thefabric to form a coaxial structure. Threads 1308 are woven in the fabricin the weft direction and may be conductive or nonconductive. In regionPQ, the twisting of threads 1302, 1304, and 1306 is preferably stoppedso that the threads run parallel to each other to form floats. Theseparallel floats may be used for selective electrical connection anddisconnection with orthogonal threads at crossover points or forelectrical device attachment, in the manner described above.

Knitted Structures

In addition to coaxial and twisted pair structures formed simultaneouslywith weaving a fabric, the present invention also includes coaxial andtwisted pair structures formed simultaneously with knitting a fabric.Such structures can be produced on knitting machines using any of theknitting processes (for example, warp knitting or weft knitting). Inwarp knitting, lateral translation of any thread is possible and thiscan be used for the formation of twisted pair and coaxial structures onthe knitting machine itself. Warp knitting consists of threads passingup the length of the fabric, with each thread intersecting with thethread on each side as shown in FIG. 14. In FIG. 14, a warp-knittedfabric 1400 includes warp knitted threads 1402. One of the threads 1402is highlighted to illustrate its interconnection with neighboringthreads. This fabric has the same appearance on each side, does notladder, and is difficult to unravel.

FIG. 15 illustrates an example of a twisted pair structure formed usingwarp knitting according to an embodiment of the present invention. InFIG. 15, a fabric-based signal transmission system 1500 includes warpknitted threads 1502, 1504, and 1506. Threads 1502 and 1504 may beinsulated conductive threads. Threads 1506 may be conductive ornonconductive. Threads 1502 and 1504 are warp knitted to each other toform a twisted pair structure. In operation, thread 1502 may beconnected to a signal source and thread 1504 may be connected to groundor vice-versa. In another mode of operation, threads 1502 and 1504 maybe oppositely driven by an AC signal source. Connecting one of theconductive threads to ground and the other thread to a signal sourceimproves signal integrity in a fabric-based electrical network becausethe ground conductor blocks electromagnetic field lines emanating fromsignal conductors. Driving conductive threads of a twisted pairstructure with equal but opposite AC signals results in common modenoise rejection. Either mode of operation is intended to be within thescope of the invention.

In addition to twisted pair structures, coaxial structures can also beformed while the threads that form the coaxial structures are being warpknitted into a fabric. FIG. 16 illustrates and example of a warp knittedfabric-based signal transmission system including a coaxial structureaccording to an embodiment of the present invention. Referring to FIG.16, a warp-knitted fabric-based signal transmission system 1600 includesinsulated conductive threads 1602, 1604, and 1606 being warp knitted toeach other to form a coaxial structure and threads 1608, which may beconductive or nonconductive. In operation, thread 1602 may be connectedto an AC signal source and threads 1604 and 1606 may be connected toground. Because grounded threads 1604 and 1606 surround conductivethread 1602, electric fields produced by other conductors will have areduced effect on signals on thread 1602. Similarly, electric fieldsproduced by thread 1602 will have a reduced effect on signals on othersignal carrying conductors. As a result, signal-carrying conductors canbe placed closer to each other in a fabric-based signal transmissionsystem, increasing the potential device density and thereby increasingthe functionality of garments incorporating such devices.

Weft Knitting can also be used to form twisted structures. FIG. 17illustrates an example of a twisted pair structure formed using weftknitting according to an embodiment of the present invention. Referringto FIG. 17, a weft-knitted fabric-based signal transmission system 1700includes insulated conductive threads 1702 and 1704 being weft knittedto each other to form a twisted pair structure. Conductive threads 1702and 1704 are also weft-knitted to threads 1706, which may be conductiveor nonconductive. The twisted pair structure formed by weft knittedthreads 1702 and 1704 may be formed on a knitting machine at the timethe fabric is created—thus decreasing the time to incorporate suchstructures into a fabric over techniques that require the twisted pairstructure to be formed in advance of incorporating the structure into afabric.

In one exemplary mode of operation, thread 1702 may be connected to asignal source and thread 1704 may be connected to ground, or vice-versa.In this mode of operation, thread 1704 blocks electromagnetic fieldsemanating from signal carrying thread 1702 from adversely affectingsignals on other conductors. In addition, ground thread 1704 reduces theeffect of electromagnetic fields from other conductors on the signal onsignal carrying thread 1702. In an alternate mode of operation, threads1702 and 1704 may be oppositely driven by and AC signal source. In thismode of operation, noise common to both threads (common-mode noise) maybe rejected.

In addition to being used to form twisted pair structures, weft knittingcan also be used to form coaxial structures. FIG. 18 illustrates anexample of a coaxial structure formed using weft knitting according toan embodiment of the present invention. In FIG. 18, a weft-knittedfabric-based signal transmission system 1800 includes insulatedconductive threads 1802, 1804, and 1806 being weft knitted to each otherto form a coaxial structure. Conductive threads 1802, 1804, and 1806 arealso weft knitted to threads 1808 to form a fabric. Threads 1808 may beconductive or nonconductive. Because the coaxial structures formed bythreads 1802, 1804, and 1806, can be formed at the time that the fabricis being knitted, the time required to produce garments including thesestructures is reduced.

In operation, thread 1802 may be connected to a signal source, andthreads 1804 and 1806 may be connected to ground. Because groundedthreads 1804 and 1806 block electromagnetic fields, signals on otherconductors near thread 1802 will have a reduced effect on the signal onthe signal on thread 1802 and vice-versa. As a result, signal-carryingconductors can be placed closer together in a garment, device densitycan be increased, and the functionality of fabric-based electricalcircuits can also be increased.

While FIGS. 3 and 4 above illustrate weaving of the coaxial and twistedpair structures illustrated in FIGS. 1 and 2 into a fabric, the coaxialand twisted pair conductive yarn structures illustrated in FIGS. 1 and 2can be knitted into a fabric. FIG. 19 illustrates exemplary warpknitting of coaxial conductive yarn structure 100 into a fabric. In FIG.19, a fabric-based signal transmission system 1900 includes a conductiveyarn 1902 and yarns 1904, which may be conductive or nonconductive. Inthe illustrated example, conductive yarn 1902 may be similar instructure to coaxial conductive yarn structure 100. That is, yarn 1902may include an inner conductor 102 having a plurality of conductivestrands being twisted together, an insulating layer 104 surrounding theconductive strands, and an insulated outer conductor 106. In operation,conductor 102 may be connected to a signal source and conductor 106 maybe connected to ground, resulting in improved signal integrity.

In addition to warp knitting, coaxial conductive yarn structure 100 canalso be weft-knitted into a fabric. FIG. 20 illustrates an example inwhich coaxial conductive yarn structure 100 is weft-knitted in a fabric.In FIG. 20, a fabric-based signal transmission system 2000 includes aconductive yarn 2002 being weft knitted into a fabric with a pluralityof other yarns 2004. In this example, conductive yarn 2002 may besimilar in structure to coaxial conductive yarn structure 100 describedabove. In operation, conductor 102 may be connected to a signal sourceand conductor 106 may be connected to ground, resulting in improvedsignal integrity in weft-knitted fabric-based circuits.

As stated above, twisted pair conductive yarn structure 200 illustratedin FIG. 2 can also be knitted into a fabric. FIG. 21 illustrates anexample of a fabric-based signal transmission system in which twistedpair conductive yarn structure 200 is weft knitted in a fabric. In FIG.21, a fabric-based signal transmission system 2100 may include aconductive yarn 2102 being warp knitted in a fabric with a plurality ofyarns 2106. In the illustrated example, conductive yarn 2102 is similarin structure to twisted pair conductive yarn structure 200 illustratedin FIG. 2. That is, conductive yarn 2102 may include first and secondconductive yarns 202 being twisted together to form a helical structure.Each yarn 202 is preferably surrounded by an insulating layer 204 toprevent short-circuiting. In operation, one conductor 202 may beconnected to a signal source, and the other conductor 202 may beconnected to ground. Alternatively, conductors 202 may be oppositelydriven to reject common mode noise.

In addition to warp knitting, twisted pair conductive yarn structure 200can be weft-knitted into a fabric. FIG. 22 illustrates a fabric-basedsignal transmission system in which twisted pair conductive yarnstructure 200 is weft knitted in a fabric. In FIG. 22, a fabric-basedsignal transmission system includes a conductive yarn 2202 being weftknitted in a fabric with a plurality of additional yarns 2204.Conductive yarn 2202 may be similar in structure to twisted pairconductive yarn structure 200 described above. Yarns 2204 may beconductive or nonconductive. In operation, the conductors of yarnstructure 2202 may be oppositely driven. Alternatively, one conductor ofyarn 2200 may be connected to a signal source and the other conductormay be grounded, as described above.

In the examples illustrated in FIGS. 3 and 4, coaxial and twisted pairconductive yarn structures 100 and 200 are plain woven into a fabric.However, the present invention is not limited to plain weaving thesestructures into a fabric and other weaves, such as Twill, Basket, Satin,or Sateen could be used. In an alternate embodiment of the invention,these structures may be leno-woven into a fabric with other similar ordifferent yarn structures to form additional coaxial or twisted pairstructures and further improve signal integrity.

Similarly, in the examples illustrated in FIGS. 19-22, single coaxialand twisted pair yarn structures 100 and 200 are warp or weft knittedinto a fabric. However, the present invention is not limited to knittingsingle structures 100 or 200 into a fabric. In an alternate embodimentof the invention, multiple coaxial or twisted pair structures may beknitted together in a fabric to form additional coaxial and twisted pairstructures as the fabric is being knitted.

Structures Involving Placement of Ground Lines and Planes

In a fabric-based circuit board, it is preferable that signal lines besurrounded by ground lines—one on each of its sides and running parallelto it. FIG. 23 illustrated an example of a fabric-based signaltransmission system where the signal carrying threads are surrounded byground threads according to an embodiment of the present invention.Referring to FIG. 23, a fabric-based signal transmission system 2300includes an insulated conductive thread 2302 surrounded on both sides byinsulated conductive threads 2304. Similarly, insulated conductivethread 2308 is surrounded on both sides by conductive threads 2304.Conductive threads 2302 and 2308 may be signal-carrying conductors andconductive threads 2304 may be connected to ground. Because conductivethreads 2304 are connected to ground, crosstalk between conductivethread 2302 and neighboring conductive thread 2308 is reduced. Theremaining threads 2306 illustrated in FIG. 23 are nonconductive.

In FIG. 23, conductive thread 2302 is surrounded on two sides bygrounded conductors 2304 in a two-dimensional fabric-based circuit.Transmission line system 2300 may be similar to the structure ofcoplanar waveguides with signal conductor 2302 surrounded by groundedconductors 2304. That is, grounded conductive threads 2304 can also bemultiple non-insulated parallel conducting threads in direct contactwith each other to form wide grounded conducting structures surroundingsignal carrying conducting threads 2302 as in a coplanar waveguide likestructure. In a three-dimensional fabric-based circuit, conductivethread 2302 may be surrounded on four sides by grounded conductingelements—from above, below, and from both sides in the plane in whichconductive thread 2302 is located.

The methods and systems for improving signal integrity in fabric-basedsignal transmission systems may be used to form single or multi-layeredelectrical circuits. FIGS. 24A and 24B illustrate examples ofmulti-layered fabric-based circuits in which the fabric-based signaltransmission systems of the present invention may be utilized. In FIGS.24A and 24B, a multi-layered signal transmission system 2400 includes aplurality of layers for forming a woven electrical network. These layerscan be different fabrics stacked together (with or without a stitch) orcould be different layers of a single multilayered fabric structuredeveloped on a loom. In the illustrated example, these layers include aconductive layer 2402, an insulating layer 2404, a second conductivelayer 2406, a second insulating layer 2408, and a third conductive layer2410. Conductive layers 2402 and 2410 may be signal-carrying layerssimilar in structure to the fabric-based signal transmission systemillustrated in FIG. 23. Insulating layers 2404 and 2408 may include aplurality of nonconductive threads woven or knitted together to form abarrier between adjacent conductive layers. Conductive layer 2406 may bemade entirely of conductive threads to form an electromagnetic shieldbetween conductive layers 2402 and 2410.

In FIG. 24B, it can be seen that in operation, layers 2402-2410 arelocated on top of each other, resulting in an increased chance ofcrosstalk between layers. However, because layer 2406 is preferablygrounded, inter-layer crosstalk is reduced. Using a ground plane canalso reduce simultaneous switching noise (SSN). The multilayered fabricstructures with signal carrying layers and ground plane layers aresimilar to some transmission line structures in conventional circuitboards and integrated circuits, such as but not limited to microstriplines and striplines.

The present invention is not limited to forming multi-layered wovencircuits. Any combination of woven layers, knitted layers, or knittedand woven layers is intended to be within the scope of the invention.

Braided and Other Coaxial Yarn Structures and Fabric Woven or Knittedfrom such Structures

Although the examples described above relate primarily to wrapped ortwisted thread or yarn structures, the present invention is not limitedto such structures. In an alternate embodiment of the invention,conductive yarn structures may be braided. FIG. 25 illustrates anexample of a coaxial conductive yarn structure including a braided outerconductor according to an embodiment of the present invention. In FIG.25, a coaxial conductive yarn structure includes an inner conductor 2502including a plurality of strands being twisted together, an insulatinglayer 2504, and a braided outer conductor a braided outer conductor2506. Examples of conductive strand material suitable for use with thepresent invention include copper, steel, gold, aluminum, silver, iron,any of the alloys from the above mentioned materials, and conductivepolymers (inherently conductive polymeric materials, such aspolypyrrole, polyacetylene, polythiophene and polyaniline, dopedconductive polymeric materials, carbon black-doped/impregnated polymericyarns, metal coated polymeric yarns or fibers and conductive yarns ofall different kinds). Insulating layer may be made up of materials, suchas polyvinylchloride, rubber, rubber forming polymers, includingpolyisoprene, polybutadiene, polychloroprene, polyisoutylene,polyesters, polyolefins, and polyamides.

Braided coaxial conductive yarn structures 2500 can be woven into afabric to form a fabric-based signal transmission system. FIG. 26illustrates an example of a fabric-based signal transmission systemincluding braided coaxial conductive yarn structures according to anembodiment of the present invention. Referring to FIG. 26, afabric-based signal transmission system 2600 includes braided coaxialconductive yarn structures 2500 woven into a fabric with yarns 2602.Yarns 2602 may be or nonconductive. If yarns 2602 are conductive, theyare preferably insulated. Inner conductive yarn 2502 of one ofconductive yarn structures 2500 is connected to a signal source 2604.The outer braids of structures 2500 are preferably connected to ground2606. Because the outer braids of structures 2500 are grounded,crosstalk between adjacent structures 2500 is reduced. Moreparticularly, when an AC signal is applied to inner conductive yarn 2502of one or both of coaxial conductive yarn structures 2500, outer braids2506 of braided coaxial conductive yarn structures 2500 blockelectromagnetic fields emanating from the inner conductive yarn 2502connected to signal source 2604.

A braided coaxial conductive yarn structure can be knitted into a fabricto form a fabric-based signal transmission system with improved signalintegrity characteristics. FIG. 27 illustrates a fabric-based signaltransmission system in which a braided coaxial conductive yarn structureis knitted into a fabric according to an embodiment of the presentinvention. In FIG. 27, braided coaxial conductive yarn structure 2500 iswarp knitted into a fabric with other yarns 2702, which are preferablynonconductive. As with the embodiment illustrated in FIG. 26, thebraided outer conductor of yarn 2500 is preferably grounded to improvesignal integrity for the inner conductor. Because the braided outerconductor is grounded, yarn structures, such as structure 2500 can beplaced close together in a fabric without adversely affecting eachother.

In addition to warp knitting, braided coaxial conductive yarn structure2500 may also be weft knitted into a fabric. FIG. 28 illustrates anexample of a braided coaxial conductive yarn structure being weftknitted in a fabric. In particular, a fabric-based signal transmissionsystem 2800 includes braided coaxial conductive yarn structure 2500being weft knitted with other yarns 2802 in a fabric. Yarns 2802 arepreferably nonconductive. In this configuration, the outer conductor ofyarn structure 2500 is preferably connected to ground, and the innerconductor is preferably connected to a signal source. Because the outerconductor is grounded, electromagnetic fields have a reduced effect onthe signal on the inner conductor. In addition, the signal on the innerconductor of braided conductive yarn structure 2502 will have a reducedeffect on other conductors. As a result, braided coaxial conductive yarnstructures can be placed closer together, and fabric-based circuitdensity is increased.

Although in the examples illustrated above, the outer conductor incoaxial conductive yarn structures is either wrapped or braided onto theinsulating layer the surrounds the inner conductor, the presentinvention is not limited to such an embodiment. In an alternateembodiment, an outer conductive layer may be coated or sputtered with aconductive layer using a conductive material that adheres on to theinsulation around the first conductor) to form a coaxial yarn. Thisstructure can also be woven or knitted to form fabric-based circuitswith reduced crosstalk noise.

In the examples set forth above, conductive yarn structures aredescribed as containing metallic fibers being twisted together to form asingle conductor with an insulating layer surrounding the conductor anda second conductor surrounding the insulating layer. In an alternateembodiment of the invention, a conductive yarn structure may include acore of coaxial monofilament yarn/fiber produced by fiber spinning of astructure having a conductive material as the core (i.e., made frominherently conductive polymeric materials, such as polypyrrole,polyacetylene, polythiophene and polyaniline, doped conductive polymericmaterials, carbon black-doped/impregnated polymeric material, polymericmaterial containing metal particles and any other kind of spinnableconducting material), an insulating material surrounding the core, and aconductive material covering the insulation. This yarn structure canalso be woven or knitted to form fabric-based circuits with reducedcrosstalk noise.

Braided Yarn Structures Developed from Coaxial and Twisted Pair YarnStructures and Fabric Woven or Knitted from Such Structures

Braided conductive yarn structures can be developed from wrapped coaxialconductive yarn structures described above. FIG. 29 illustrates braidingof coaxial yarn structures 100 into a single braided conductive yarn. InFIG. 29, a braided conductive yarn structure 2900 includes wrappedcoaxial conductive yarns 100. Different electronic devices, such assensors, microphones, and integrated circuits may be connected to theinner conductor 102 of the different coaxial yarns 100 in this braidedyarn structure 2900. Outer conductors 106 of coaxial conductive yarnstructures 100 may be connected to ground.

Braided conductive yarn structures can also be developed from twistedpair conductive yarn structures described above. FIG. 30 illustratesbraiding of twisted pair yarn structures 200 into a single braidedconductive yarn. In FIG. 30, a braided conductive yarn structure 3000includes twisted pair conductive yarn structures 200. Differentelectronic devices, such as sensors, microphones, and integratedcircuits can be connected to one of the two conductive yarns 202 of thedifferent twisted pair conductive yarn structures 200 in braided yarnstructure 3000. The other conductive yarn 202 of twisted pair yarnstructures 200 may be connected to ground.

Braided conductive yarn structures can be also developed from braidedcoaxial conductive yarn structures described above. FIG. 31 illustratesbraiding of braided coaxial yarn structures 2500 into a single braidedconductive yarn. In FIG. 31, a braided conductive yarn structure 3100includes braided coaxial conductive yarns 2500. Different electronicdevices, such as sensors, microphones, and integrated circuits, can beconnected the inner conductor 2502 of the different coaxial yarns 2500in this braided yarn structure 3100. Braided outer conductors 2506 ofthe coaxial yarns 2500 can be connected to ground.

Conductive braided yarn structures 2900, 3000, and 3100 can be developedon a standard braided yarn manufacture machine. The advantage of usingbraided conductive yarn structures 2900, 3000, and 3100 is that theyallow a large number of conductive yarns to be incorporated into onebraided yarn structure. Thus, a very high density of coaxial and twistedpair yarns in one conductive braided yarn structure can be achieved.These conductive braided yarn structures can be integrated into a fabric(by weaving or knitting them into a fabric) thereby increasing thedensity of coaxial and twisted pair threads in the fabric.

Another advantage of conductive braided yarn structures 2900, 3000, or3100 is that small-sized electronic devices, such as sensors,microphones, and integrated circuits, can be connected to the coaxial ortwisted pair conductors of the conductive braided yarn in a manner suchthat they are hidden and protected in the core of the braided structures2900, 3000, or 3100. Incorporating electronic devices in the core ofbraided yarn structures 2900, 3000, or 3100 may be possible when thebraided conductive yarn structure has a hollow core and the electronicdevices are smaller than the hollow region in the core of the braidedyarn structures 2900, 3000, or 3100. Incorporating electronic deviceswithin the core of braided yarn structures 2900, 3000, or 3100 makes theelectronic devices invisible on the surface of the fabric into whichbraided yarns 2900, 3000, or 3100 are integrated. Moreover, theelectronic devices can first be attached to the twisted pair or coaxialyarns of the conductive braided yarn structures 2900, 3000, or 3100 andthen integrate these structures into a fabric by weaving and knitting.

Braided conductive yarn structures 2900, 3000 or 3100 can be woven intoa fabric to form a fabric-based signal transmission system. FIG. 32illustrates an example of a fabric-based signal transmission systemincluding braided conductive yarn structures according to an embodimentof the present invention. Referring to FIG. 32, a fabric-based signaltransmission system 3200 includes conductive braided yarn structures2900, 3000 or 3100 woven into a fabric with yarns 3204. Yarns 3204 maybe conductive (with an insulating layer around the conductive yarns) ornonconductive.

Braided conductive yarn structures 2900, 3000 or 3100 can also be warpknitted into a fabric to form a fabric-based signal transmission system.FIG. 33 illustrates an example of a fabric-based signal transmissionsystem including braided conductive yarn structures according to anembodiment of the present invention. Referring to FIG. 33, afabric-based signal transmission system 3300 includes conductive braidedyarn structures 2900 or 3000 or 3100 warp knitted into a fabric withyarns 3304. Yarns 3304 may be conductive (with an insulating layeraround the conductive yarns) or nonconductive.

Braided conductive yarn structures 2900, 3000 or 3100 can also be weftknitted into a fabric to form a fabric-based signal transmission system.FIG. 34 illustrates an example of a fabric-based signal transmissionsystem including braided conductive yarn structures according to anembodiment of the present invention. Referring to FIG. 34, afabric-based signal transmission system 3400 includes conductive braidedyarn structures 2900, 3000 or 3100 weft knitted into a fabric with yarns3404. Yarns 3404 may be conductive (with an insulating layer around theconductive yarns) or nonconductive.

Experimental Results

In experiments using yarn structures of the present invention, thecrosstalk on adjacent lines using yarn structures according to thepresent invention is significantly reduced over nongrounded conductiveyarn structures. For example, the reduction in crosstalk noise appearingon a quiet line in one of the experiments was reduced by a factor ofnearly five. Because the present invention greatly reduces crosstalk inwoven and other fabric-based networks, conductive yarn structures can bespaced more closely to each other in fabric-based networks.Consequently, component density can be increased without increasingcircuit board area.

Thus, the present invention includes conductive yarn, thread, and fabricstructures with improved signal integrity characteristics. In addition,the present invention includes methods for making yarn and threadstructures while these structures are being knitted or woven into afabric. Such methods decrease the time required to produce fabric-basedelectric circuits and facilitate creation of regions in the threads forelectrical device interconnection and disconnection.

It will be understood that various details of the invention may bechanged without departing from the scope of the invention. Furthermore,the foregoing description is for the purpose of illustration only, andnot for the purpose of limitation—the invention being defined by theclaims.

1. A twisted pair conductive yarn structure comprising: (a) a firstconductive yarn having a plurality of conductive strands being twistedtogether; (b) a second conductive yarn having a plurality of conductivestrands being twisted together, the second conductive yarn being twistedtogether with the first conductive yarn to form a helical structure; and(c) at least one insulating layer surrounding at least one of theconductive yarns for electrically isolating the first and secondconductive yarns from each other.
 2. The twisted pair conductive yarnstructure of claim 1 wherein the conductive strands comprise aconductive material selected from a group including metals, alloys, andconductive polymers.
 3. The twisted pair conductive yarn structure ofclaim 1 wherein the insulating layer comprises an electricallyinsulating material selected from a group including polyvinylchloride;rubber; rubber forming polymers, including polyisoprene, polybutadiene,polychloroprene, and polyisobutylene; polyesters; polyolefins; andpolyamides.
 4. The twisted pair conductive yarn structure of claim 1wherein the insulating layer is substantially uniform in thickness.
 5. Awoven electrical network comprising: (a) a first twisted pair conductiveyarn structure being woven into a fabric in a first direction, the firsttwisted pair conductive yarn structure including first and secondconductive yarns and at least one insulating layer for electricallyisolating the first and second conductive yarns from each other, thefirst and second conductive yarns being twisted together to form ahelical structure, the second conductive yarn being connected to ground;(b) a second twisted pair conductive yarn structure being woven into thefabric in the first direction and being spaced from the first twistedpair yarn structure, the second twisted pair conductive yarn structureincluding first and second conductive yarns and at least one insulatinglayer for electrically isolating the first and second conductive yarnsfrom each other, the first and second conductive yarns being twistedtogether to form a helical structure, the second conductive yarn beingconnected to ground; and (c) an AC signal source being connected to thefirst conductive yarn of the first twisted pair conductive yarnstructure for sending an AC signal over the first twisted pairconductive yarn structure, wherein the grounded second conductive yarnsof the first and second twisted pair conductive yarn structures blockelectromagnetic fields emanating from the first conductive yarn of thefirst twisted pair conductive yarn structure and thereby reducecrosstalk between the first and second twisted pair conductive yarnstructures.
 6. The woven electrical network of claim 5 whereinconductive yarns of the first and second twisted pair conductive yarnstructures each include a plurality of conductive strands being twistedtogether with each other.
 7. The woven electrical network of claim 6wherein the conductive strands comprise a conductive material selectedfrom a group including metals, alloys, and conductive polymers.
 8. Thewoven electrical network of claim 5 wherein the insulating layerscomprise an electrically insulating material selected from a groupincluding polyvinylchloride; rubber; rubber forming polymers, includingpolyisoprene, polybutadiene, polychloroprene, and polyisobutylene;polyesters; polyolefins; and polyamides.
 9. The woven electrical networkof claim 5 wherein the insulating layers are substantially uniform inthickness.
 10. The woven electrical network of claim 5 wherein the firstand second twisted pair conductive yarn structures are spaced from eachother in the fabric by a predetermined distance.
 11. The wovenelectrical network of claim 10 wherein the predetermined distancesranges from about one hundredth of an inch to no more than about oneinch.
 12. The woven electrical network of claim 5 comprising a pluralityof nonconductive yarns being woven in the fabric with the twisted pairconductive yarn structures.
 13. The woven electrical network of claim 12wherein the nonconductive yarns each comprise a material selected from agroup including polyamides, including nylon; polyurethane; polyimides;polyesters; acrylics, acetate materials; viscose materials; and naturalfibers, including wool, silk, and cotton.
 14. The woven electricalnetwork of claim 5 wherein the first and second twisted pair conductiveyarn structures comprise warp yarns.
 15. The woven electrical network ofclaim 5 wherein the first and second twisted pair conductive yarnstructures comprise weft yarns.
 16. A method for making a fabric-basedsignal transmission system, the method comprising: (a) weaving aplurality of nonconductive threads together to form a fabric; (b)twisting first and second insulated conductive threads together; and (c)while twisting the first and second insulated conductive threadstogether, leno-weaving the first and second conductive threads into afirst region of the fabric.
 17. The method of claim 16 whereinperforming steps (b) and (c) includes weaving the first and secondconductive threads into the fabric in a first direction whilesimultaneously twisting the threads around adjacent nonconductivethreads extending in a second direction in the fabric transverse to thefirst direction
 18. The method of claim 16 wherein performing step (c)includes using a Jacquard loom equipped with leno headles.
 19. Themethod of claim 16 wherein leno-weaving the first and second conductivethreads into the fabric includes interlocking the first and secondconductive threads with the nonconductive threads such that, in thefirst region, the first conductive thread is always on a first side ofeach of the nonconductive threads and the second conductive thread isalways on a second side of each of the nonconductive threads, therebyforming a bottom doup leno weave.
 20. The method of claim 16 whereinleno-weaving the first and second conductive threads into the fabricincludes interlocking the first and second conductive threads with thenonconductive threads such that, in the first region, the firstconductive thread alternates between first and second sides of adjacentnonconductive threads and the second conductive thread alternatesbetween the second and first sides of the adjacent nonconductivethreads.
 21. The method of claim 16 comprising, in a second region ofthe fabric, ceasing steps (b) and (c) and weaving the first and secondinsulated conductive threads into the fabric.
 22. The method of claim 21wherein weaving the first and second insulated conductive threads intothe fabric includes skipping at least one of the nonconductive threadsand thereby creating a float to facilitate interconnection ordisconnection with electrical devices.
 23. The method of claim 16wherein the first and second conductive threads form a twisted pairstructure.
 24. The method of claim 16 comprising, concurrently with step(c), leno weaving a third conductive thread into the fabric with thefirst and second conductive threads to form a coaxial structure.